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Tactical Machining question - Pic's are up


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I'm working on assembling my TM lower and I've finished everything but I've  discovered that the bolt release pin/screw from the DPMS 308 LPK does not fit into the hole in the side of the receiver.  ???

I mean the "shaft" part won't even fit into the threaded part of the hole in the receiver, there's noway it's going to fit into the smaller diameter 'non-threaded' part of the receiver/bolt catch interface (although it does fit in the pivot hole in the bolt catch). help.gif

Also, I didn't find any kind of notice about this "issue" on the TM website, only the claim that their "lower receiver is compatible with DPMS platform upper receivers".

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Have you turned it around to see if the  "head" of the pin is correctly threaded so that you can screw it into the receiver? If not, Maybe you can try to find something laying around the house that does thread into the receiver so you can figure out if the problem is the pin or the receiver.

I've not worked on these receivers but I'm thinking that ideally you'd like to have it threaded to the correct standard size, so if it turns out the receiver is the problem you may need to carfully drill and tap it. If you have to, be sure to put plenty of tape on the side of the receiver to protect it while you do the work.

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I have the TM lower and it came with its own pin and set screw, if yours didn't come with these items then you should contact TM and let them know. I'm sure they will get you what you need.

Nice Lower, I love mine!  <thumbsup>

This makes so much sense, as the DPMS pin/screw is so so far off sized.

Thanks so much for the info!!hethan.gif

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You will find that POF rifles have the smaller size also . Just to clarify , its the same threading into the receiver ,but where the pin part of the screw goes into the far side of the pin/screw hole, for the bolt catch , the DPMS is larger.

I turned down one to fit until I got a pin/screw from POF w/ an extra pin. I have both pins & can get measurements & photos later.

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Called them this morning(mon) and they sent out in the mail the "308 AR lower small parts kit", which includes a dowel pin for the bolt catch and a set screw to hold the dowel pin.

The kit also has a set screw for the rear take-down pin detente and spring. I figured out during the build that there was another 'issue' with the take-down pin, but I had just taken an extra detente spring and cut it down to fit with enough tension.

I am kind of miffed that I didn't notice the threading in the hole for the rear spring in the first place.cookoo.gif

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Now that's different , I kinda like the idea of a pin with a set screw as a keeper.

There are a few manufacturers using a short spring & set screw for the safety detent & disassembly pin, good ideas also.

The parts arrived today.  :) I'll take some comparison pics on the weekend.

However, there was also a 'installations tips' sheet and for the bolt catch parts it says "do not test fit it, it may be difficult to get back out"  :D

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The parts arrived today.  :) I'll take some comparison pics on the weekend.

However, there was also a 'installations tips' sheet and for the bolt catch parts it says "do not test fit it, it may be difficult to get back out"  :D

Well that would suck . Wonder if a good strong magnet would help in that case.

Yes , Photo's.

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  • 2 weeks later...

Well, I'm still a beginner at doing my own pictures, so sorry about their quality. <dontknow>

Here is a comparison; the DPMS screw/pin is on the left and the allen wrench it uses, and on the right is the silver dowel pin and set screw from TM and the smaller size allen wrench.

2011_01011LM0012.jpg

Here is the dowel pin going in

[img width=810 height=607]http://i403.photobucket.com/albums/pp112/Lon_Moer/2011_01011LM0009.jpg

Here's the set screw for the rear take down pin detent and spring. The set screw allowed me to set the tension on the spring and adjust how tight I wanted the take down pin to be.

[img width=810 height=607]http://i403.photobucket.com/albums/pp112/Lon_Moer/2011_01011LM0003.jpg

And complete so far.

[img width=810 height=607]http://i403.photobucket.com/albums/pp112/Lon_Moer/2011_01011LM0002.jpg

I just got my upper receiver from Red-X Arms, some PMAGS and some barrel parts. I'll post up some newer pictures soon. Thanks all! <thumbsup>

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I certainly like the idea of these pins and springs being held in place with set screws. makes it easier to take them apart without having springs disappearing under the bench. I've never much liked dealing with the installation and removal of roll pins in the aluminum AR receivers. Of course, this is another instance where there is no standard for the pins, so you pretty much have to learn what each MFG decided to use, and if you own a number of guns from different MFG's you need to have several different parts kits on hand if you want spares for each of your guns.

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